Inkjet-printing devices, which are generally referred to as fluid-ejection devices, have become popular in residential, business, and industrial settings. They have proven to be a cost-effective manner by which to output black-and-white and color images onto media, such as paper and other types of media. Inkjet-printing devices generally work by ejecting ink from a number of inkjet-printing nozzles onto the media. In a thermal inkjet-printing device, a resistive element within a nozzle is heated, causing ink to be ejected from the nozzle. The ink is more generally fluid, and the inkjet-printing nozzles are more generally fluid-ejection nozzles.
The inkjet-printing nozzles of inkjet-printing devices occasionally clog, inhibiting their ability to eject ink. The ink may dry over an inkjet-printing nozzle, such that a spitting or a wiping process is performed to clear the nozzle so that it can again properly eject ink. When one or more of the inkjet-printing nozzles of an inkjet-printing device clogs, the quality of the resulting output on media may degrade. For example, streaks may become evident on the media, and where the image being output onto the media includes text, the text may become illegible.
Determining whether an inkjet-printing nozzle is clogged is usually an offline process that cannot be performed while the inkjet-printing device is being used to output images onto media. Some inkjet print jobs may take hours or days to complete, and usually cannot be interrupted once started to perform an offline process. Thus, such print jobs may mean that the inkjet-printing device is not able to determine whether nozzles have clogged for hours or days, while the print jobs are being completed.